1. Field of the Invention
The present invention relates to a seat belt retractor for use in a vehicle. In particular, the present invention relates to a seat belt retractor having a mechanism which, in response to a predetermined amount of seat belt webbing withdrawal, moves a member to a position in which further withdrawal of the seat belt webbing is blocked.
2. Description of the Prior Art
Seat belt retractors having a mechanism which, in response to a predetermined amount of seat belt webbing withdrawal, moves a member to a position blocking further withdrawal of seat belt webbing from the retractor are known. Such a mechanism is referred to as a "cinch mechanism". A seat belt retractor having a cinch mechanism is useful for securing an article, such as a package or a child seat, to a vehicle seat. Although a cinch mechanism is actuated to block withdrawal of seat belt webbing from the retractor after a predetermined amount of webbing has been withdrawn, seat belt webbing can still be wound onto the retractor.
U.S. Pat. No. 4,436,255 discloses a vehicle sensitive seat belt retractor having a cinch mechanism. The cinch mechanism includes a cam member which rotates in response to rotation of a belt takeup shaft. When a predetermined amount of seat belt webbing is withdrawn, the cam member rotates to a predetermined position and moves a follower. The follower moves a pawl into engagement with a ratchet wheel connected to the takeup shaft. The pawl then blocks further rotation of the ratchet wheel and takeup shaft in the belt withdrawal direction.
U.S. Pat. No. 4,518,132 also discloses a vehicle sensitive seat belt retractor having a cinch mechanism. Upon withdrawal of the seat belt webbing, a part of the webbing engages and pivots a lever. Pivoting of the lever causes a spring to move a pawl into engagement with a ratchet wheel connected with a spool of the retractor. Further rotation of the spool in the belt withdrawal direction is, thus, blocked but rotation of the spool in a belt retraction direction is permitted.